GB1588363A

GB1588363A - Process for preparing paraffin sulphonic acids and sulphonates

Info

Publication number: GB1588363A
Application number: GB4209377A
Authority: GB
Original assignee: ATO Chimie SA
Current assignee: ATO Chimie SA
Priority date: 1976-10-13
Filing date: 1977-10-10
Publication date: 1981-04-23
Also published as: DE2745691A1; SE441092B; SE7711502L

Description

(54) AN IMPROVED PROCESS FOR PREPARING PARAFFIN SULPHONIC ACIDS AND SULPHONATES (71) We, ATO CHIMIE, a French Company, of Tour Aquitaine, 92400 Courbevoie, France, do hereby declare the invention, for which we pray that a Patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The present invention concerns an improved process for separating paraffin sulphuric acids contained in an untreated sulphuric solution which also includes, in addition to these acids, sulphuric acid, water and non-sulphonated paraffins.

Certain sulphonic acids derived from hydrocarbons, and more specifically those obtained from linear paraffins, are biodegradable, even at low temperatures.

This makes such products particularly suitable for use as detergents, since they can be discharged into rivers of the sea without causing any serious pollution of the aqueous environment that could harm aquatic flora and fauna.

These paraffin sulphuric acids can be produced by various methods, and in particular by the "sulphoxidation method", in which sulphur dioxide and oxygen are made to act simultaneously of paraffins, in particular linear paraffins, under the influence of photoactive radiation. A suitable amount of water is added, to extract the paraffin sulphuric acids from the reaction mixture.

The untreated sulphonic acid solution extracted from the reaction zone, which contains the paraffin sulphonic acids produced, sulphuric acid, water and a certain amount of unreacted paraffins, is treated in order to separate the sulphonic acids.

An existing method of performing this separation involves the addition to the reaction mixture from the sulphonation reactor of a polar light organic solvent which is immiscible with paraffins, such as methanol, ethanol or light esters, to bring about separation of the solution into a hydrocarbon phase and a paraffin-free aqueous organic phase containing the sulphonic acids and sulphuric acid in solution, and then neutralization of the aqueous organic phase by means of a suitable alkali, to precipitate the sulphuric acid as sulphate, which is then removed by filtration, and finally treatment of the aqueous organic solution with an alkaline salt, in order to salt out the sulphonic acids and/or sulphonates.

This process has proved uneconomical. because of the high consumption of alkali needed to convert the sulphuric acid into sulphate, and the serious losses of sulphonates or sulphonic acids that occur during filtration of the sulphate. In addition, use of the process on an industrial scale, which, to be economic, requires continuous filtration of the sulphate, involves difficulties arising from the possibility of frequent clogging of the filters.

Another existing process consists of removing part of the sulphuric acid contained in the reaction mixture from the sulphonation reaction before extracting the paraffin sulphonic acids. The process involves rapid evaporation of the reaction mixture by heating up to 1800C, causing.separation of the mixture into an upper layer containing the paraffins and sulphonic acids, and a lower layer of aqueous sulphuric acid, which is then removed.

This process is not completely satisfactory either, because the heating required for evaporation of the reaction mixture causes fairly marked deterioration of the sulphonic acids. affecting the quality of the final product.

According to a further existing process which is the subject of Patent No. 1,358,095. a slightly polar alcohol having at least five carbon atoms in the molecule is added to the untreated sulphonic solution in order to separate the mixture into an organic phase containing all of the paraffin sulphonic acids and an aqueous phase containing substantially all of the sulphuric acid. The organic phase is separated from the aqueous phase and treated with alkali to neutralize the sulphonic acids by forming sulphonates, and then the sulphonates are separated by evaporation of the volatile components of the neutralized organic phase, this evaporation being performed under such a temperature and pressure that the sulphonates are in a molten state.

This process has succeeded in reducing the drawbacks of the other above-mentioned existing processes. However, when carrying out the separation in a continuous manner which involves recycling the slightly polar alcohol distilling off during the evaporation of the neutralized phase, difficulties may arise in separating this alcohol from the non-sulphonated paraffins which distill off at the same time, and in obtaining an alcohol substantially free from paraffin which can thus be reused.

In has been found that in such a process certain organic solvents which are more volatile than the alcohols and therefore can be more easily separated from the paraffins were also very efficient for separating the sulphonic acids from the untreated sulphonic solution.

Further, under particular operating conditions the use of these solvents also enables the sulphuric acids to be recovered as substantially anhydrous alkaline sulphonates which can be converted into a free-flowing and non-caking white powder.

According to the present invention a process for separating paraffin sulphonic acids as the sulphonate salts from an untreated paraffin sulphonic solution which also contains sulphuric acid, and water, and optionally unreacted paraffins, and recovering these paraffin sulphonic acids as paraffin sulphonates, comprises adding to the untreated paraffin sulphonic acid solution at least one slightly polar solvent (other than an alcohol having 5 or more carbon atoms,) having a solubility in water less than 7% by weight and capable of forming an azeotrope with water, thereby separating the mixture into an organic phase containing all of the paraffin sulphonic acids and an aqueous phase containing substantially all of the sulphuric acid, then separating the organic phase from the aqueous phase and treating the separated organic phase with an alkali to neutralize the sulphonic acids by forming sulphonates and thereafter evaporating the volatile components from the neutralized organic phase, this evaporation being conducted under such a temperature and pressure that the sulphonates are in a molten state.

The slightly polar solvent is preferably selected from aliphatic or cycloaliphatic esters, ketonesters containing at least five carbon atoms. Among these compounds, those containing from 5 to 12 carbon atoms and having a solubility in water less than 5% by weight are particularly preferred. In particular the slightly polar solvents are preferably alkanones, cycloalkanones, aliphatic ethers, cycloaliphatic ethers, alkyl alkanoates, cycloalkylalkanoates, alkyl cycloalkanoates, aliphatic ketone esters which preferably have from five to 12 carbon atoms.

Suitable alkanones and cycloalkanones include for instance methyl propyl ketone, methyl iso propyl ketone. methyl isobutyl ketone, methyl n-butyl ketone, methyl nonyl ketone, di ethyl ketone, dibutylketone, di isobutyl ketone, diamylketone, cyclooctanone, cycloheptanone. Examples of suitable ethers are di isopropyl oxide, di isobutyl oxide, methyl heptyl oxide. diamyl oxide, di isoamyl oxide. The esters and ketonesters may include among others ethyl butyrate, n-butyl butyrate. amyl acetate, butylacetate, butyl acetyl acetate, isoamyl acetate. propyl acetate.

The amount of slightly polar solvent or of the mixture of such solvents to be added to the untreated sulphonic solution in order to bring out separation of the sulphonic acid, preferably ranges from 10 to 150 parts by weight per 100 parts by weight of the sulphonic solution, and more preferably from 30 to 100 parts by weight per 100 parts by weight of said solution.

When the untreated sulphonic acid solution contains some unreacted paraffins, such paraffins may be removed from the phase containing the sulphonic acids before or after separation of the sulphuric acid. by adding a polar liquid such as methanol, ethanol, a low molecular weight carboxylic acid. acetone. or a sulphoxide which solvent is water soluble but immiscable with the paraffins, and which therefore causes them to salt out.

The phase containing the sulphonic acids to which is added the polar liquid is either the untreated sulphonic acid solution. if the paraffins are removed before separation of the sulphuric acid, or the organic phase containing the sulphonic acids in solution in the slightly polar solvent, if removal of the paraffins takes place after separation of the sulphuric acid.

The amount of polar liquid to be added to the phase containing the sulphonic acids preferably ranges from 10 to 90C/c of the weight of the phase, and is more preferably equal to about 60C/c of this weight.

When the unreacted paraffins are removed from the untreated sulphonic acids solution, the polar liquid is usually separated from the paraffin-free sulphonic solution, e.g. by distillation. before treatment with the slightly polar solvent.

As stated above. the organic phase containing the paraffin sulphonic acids dissolved in the slighty polar solvent is treated by an alkali to neutralize the organic phase is submitted to evaporation to remove the volatile components thereof to obtain sulphonates, this evaporation being performed under such a temperature and pressure that the sulphonates are in the form of a molten mass which is then cooled and optionally converted to particulate form.

In a preferred embodiment of the invention, which permits recovery of the sulphonates in a substantially anhydrous form, during or after neutralization of the organic phase containing the sulphuric acids, but before evaporation of the volatile components of the neutralized organic phases, the ratio of the amount of water to the amount of slightly polar solvent in the neutralized organic phase is controlled, so that the ratio is at most equal to, and preferably less than, the corresponding ratio for the azeotrope formed by water and the slightly polar solvent.

Examples of suitable neutralizing agents are hydroxides and carbonates of alkali metals, particularly sodium and potassium and oxides, hydroxides and carbonates of alkaline earth metals, particularly calcium.

These agents may be used in solid form, or in alcoholic or aqueous solutions, in proportions at least sufficient to neutralize all the sulphonic acids, and preferably with a slight excess of the agent.

As previously indicated while neutralizing the organic phase or after the neutralization has been performed but before evaporating the neutralized phase, the ratio of the amount of water to the amount of slightly polar solvent in the neutralized phase is controlled so that the value of said ratio is at most equal to, and preferably less than the value of the corresponding ratio for the azeotrope. This control may be performed merely by determining the water content of the neutralized organic phase and if the content found is higher than the content which corresponds to the azeotrope sufficient quantity of the slightly polar solvent is added to the neutralized organic phase so that its water content is brought back to a value which does not exceed the content for said azeotrope. It is also possible to control the ratio of the amount of water to the amount of the slightly polar solvent in the neutralized organic phase by determining the water content of the organic phase to be nautralized and then adding to this phase the neutralizing agent in the most appropriate form, namely in solid form or as a solution in the slightly polar solvent or in water so that the total water content of the neutralized solution, which includes the water content of the organic phase to be neutralized together with the water content resulting from the neutralized reaction and possibly the water content from the added water if an aqueous solution of neutralizing agent is used, is at most equal to, and preferably less than the water content for the azeotrope. This control of the ratio of the amount of water to the amount of slightly polar solvent in the neutralized phase, performed either during the neutralization or after carrying the neutralization, ensures that substantially complete removal of the water is obtained during the evaporation step of the neutralized organic phase and accordingly that a substantially anhydrous sulphonate mass is produced.

The evaporation of the neutralized organic phase is carried out under pressure and temperature conditions that will ensure that the sulphonate is molten. The operation is generally performed at atmospheric pressure, though it is possible to work under a vacuum of varying force.

In a variant involving the treatment of the organic solution of the sulphonic acids in the slightly polar solvent from which the paraffins have been removed by treatment with a polar liquid after separation of the sulphuric acid, the polar liquid is recovered by distillation after the neutralization step and before evaporation of the slightly polar solvent.

The alkali metal or alkaline earth metal sulphonate collected in molten form after evaporation of the neutralized organic phase is substantially free from water, the slightly polar solvent and unreacted paraffins. It can easily be converted into a free-flowing.

practically anhydrous and non-caking white powder.

This powder can be handled easily and is particularly well-adapted to pneumatic conveyance. It can be stored without difficulty and can easily be incorporated into detergents sold commercially in powder form.

The particle size of this powder can very widely, depending on the use to which it is to be put. For normal purposes, it is preferably between 40 and 600 microns.

The powder may be prepared by any conventional process from the molten sulphonate mass. For example. the mass molten sulphonates can be solidified in the form of flakes, and the flakes ground to the particle size required in a device such as a disintegrat or with blades rotating at high speed.

The process according to the present invention is particularly applicable to the treatment of untreated sulphonic solutions resulting from sulphoxidation of normal paraffins, the molecules of which contain between 7 and 30. and preferably between 10 and 20, carbon e f n rs The invention is illustrated by, while not being confined to the following example.

Example A photochemical reactor, supplied with a mixture of C13 to C17 linear paraffins, and with water, sulphur dioxide and oxygen, produced an untreated sulphonic solution having the following composition: Sulphonic acid 20.6% by weight Sulphuric acid 8.2% by weight Non-sulphonated paraffins 31% by weight Water 41.2% by weight After any gases have been removed from this solution by conventional methods, a series of separation treatments is performed using variable amounts of one of the following slightly polar solvents: methyl propyl ketone, methylisobutylketone, di isopropyl ketone, propylacetate, butylacetate, amylacetate, isoamylacetate and ethyl butyrate.

Each separation treatment is performed as follows: The slightly polar solvent is added to 1000 g of the solution to form separate organic and aqueous phases. The mixture is stirred. then transferred to a decanting apparatus where a heavier phase consisting of an aqueous sulphuric acid solution separated out from a lighter organic phase. The sulphonic acids contained in the lighter organic phases are next neutralized by a slight excess of a 50% sodium hydroxide (12N) aqueous solution. After the neutralization step the ratio of the amount of water to the amount of slightly polar solvent in the neutralized phase is determined and if necessary adjusted so that said ratio is less than the corresponding ratio for the azeotrope which forms between water and the slightly polar solvent used.

The table hereafter shows the percentage weights of sulphuric acid salted out in the aqueous phase depending on the type and the amount (expressed in percentage by weight in relation to the untreated sulphonic solution) of slightly polar solvent used, and also the water to slightly polar solvent weight ratio in the neutralized organic phase.

The solution of sodium sulphonate in the organic phase thus obtained is then conveyed to an evaporator operating at 175"C, in which the slightly polar solvent and remaining water are removed from the sulphonate. The paraffins were then evaporated in a thin layer evaporator at a temperature of about 200"C and at a pressure of about 10-20 mm of Hg to remove all the paraffins.

The molten sulphonate leaving the evaporator has a temperature of about 200"C and a viscosity of about 50 poises. The molten sulphonate is solidified into flakes on a drum cooled internally by circulating water. The flakes obtained are then ground in a disintegrator equipped with high speed revolving blades.

The powder obtained is classified in a system of cyclones and a fraction with particle size ranging from 70 to 400 microns is recovered. larger particles being returned to the disintegrator.

The sulphonate powder, which was obtained in the various separation tests in an amount ranging from 220 to 226 g. consisted of rounded particles. This powder was white, substantially anhydrous and free from paraffins. No lumps were found to form even after prolongated storage.

TABLE % weight of sli- % sulphuric Water to solvent Slightly ghtly polar sol- acid salted weight ratio polar solvent vent in relation out in aqueous in the neutra to untreated sul- phase lized organic phonic solution phase Methylpropylketone 34 79 0.20 42 82 0.17 85 98.5 0.074 Methyl Isobutyl ketone 42 83 0.28 82 96.5 0.081 Diisopropyl ketone 37 68 0.04 75 78.5 0.04 Propylacetate 92 88 0.10 Butyl acetate 36 78 0.37 45 81 0.26 91 83 0.12 Amylacetate 44.5 84 0.24 90 89 0.11 Isoamylacetate 44 83 0.26 89 84 0.10 Ethylbutyrate 45 77 0.21 90 83 0.125 WHAT WE CLAIM IS: 1. A process for separating paraffin sulphonic acids as the sulphonate salts from an untreated paraffin sulphonic solution which also contains sulphuric acid, and water, and optionally unreacted paraffins, and recovering these paraffin sulphonic acids as paraffin sulphonates, which comprises adding to the untreated paraffin sulphonic acid solution at least one slightly polar solvent (other than an alcohol having 5 or more carbon atoms) having a solubility in water less than 7% by weight and capable of forming an azeotrope with water, thereby separating the mixture into an organic phase containing all of the paraffin sulphonic acids and an aqueous phase containing substantially all of the sulphuric acid, then separating the organic phase from the aqueous phase and treating the separated organic phase with an alkali to neutralize the sulphonic acids by forming sulphonates and thereafter evaporating the volatile components from the neutralized organic phase. this evaporation being conducted under such a temperature and pressure that the sulphonates are in a molten state.

2. A process according to Claim 1, wherein from 10 to 150 parts by weight of the slightly polar solvent is added per 100 parts by weight of the paraffin sulphonic acid solution.

3. A process according to Claim 1. wherein the slightly polar solvent is added to the sulphonic acid solution in an amount from about 30 to 100 parts by weight per 100 parts by weight of the sulphonic acid solution.

4. A process according to any preceding Claim, wherein the slightly polar solvent is an alkanone. cycloalkanone, aliphatic ether, cycloaliphatic ether, alkyl alkanoate, cycloalkylalkanoate, alkyl cycloalkanoate or aliphatic ketone ester.

5. A process according to any preceding Claim. wherein the slightly polar solvent contains from 5 to 12 carbon atoms and has a solubility in water less than 5% by weight.

6. A process according to any preceding Claim, wherein during or after neutralization of the organic phase containing the sulphonic acids dissolved therein but before evaporation of the volatile components of the neutralized organic phase, the ratio of the amount of water to the amount of slightly polar solvent in the neutralized phase is controlled so that this ratio is at most equal to the corresponding ratio for the azeotrope.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **.

TABLE % weight of sli- % sulphuric Water to solvent Slightly ghtly polar sol- acid salted weight ratio polar solvent vent in relation out in aqueous in the neutra to untreated sul- phase lized organic phonic solution phase Methylpropylketone 34 79 0.20

42 82 0.17

85 98.5 0.074 Methyl Isobutyl ketone 42 83 0.28

82 96.5 0.081 Diisopropyl ketone 37 68 0.04

75 78.5 0.04 Propylacetate 92 88 0.10 Butyl acetate 36 78 0.37

45 81 0.26

91 83 0.12 Amylacetate 44.5 84 0.24

90 89 0.11 Isoamylacetate 44 83 0.26

89 84 0.10 Ethylbutyrate 45 77 0.21

90 83 0.125 WHAT WE CLAIM IS: 1. A process for separating paraffin sulphonic acids as the sulphonate salts from an untreated paraffin sulphonic solution which also contains sulphuric acid, and water, and optionally unreacted paraffins, and recovering these paraffin sulphonic acids as paraffin sulphonates, which comprises adding to the untreated paraffin sulphonic acid solution at least one slightly polar solvent (other than an alcohol having 5 or more carbon atoms) having a solubility in water less than 7% by weight and capable of forming an azeotrope with water, thereby separating the mixture into an organic phase containing all of the paraffin sulphonic acids and an aqueous phase containing substantially all of the sulphuric acid, then separating the organic phase from the aqueous phase and treating the separated organic phase with an alkali to neutralize the sulphonic acids by forming sulphonates and thereafter evaporating the volatile components from the neutralized organic phase. this evaporation being conducted under such a temperature and pressure that the sulphonates are in a molten state.
2. A process according to Claim 1, wherein from 10 to 150 parts by weight of the slightly polar solvent is added per 100 parts by weight of the paraffin sulphonic acid solution.
3. A process according to Claim 1. wherein the slightly polar solvent is added to the sulphonic acid solution in an amount from about 30 to 100 parts by weight per 100 parts by weight of the sulphonic acid solution.
4. A process according to any preceding Claim, wherein the slightly polar solvent is an alkanone. cycloalkanone, aliphatic ether, cycloaliphatic ether, alkyl alkanoate, cycloalkylalkanoate, alkyl cycloalkanoate or aliphatic ketone ester.
5. A process according to any preceding Claim. wherein the slightly polar solvent contains from 5 to 12 carbon atoms and has a solubility in water less than 5% by weight.
6. A process according to any preceding Claim, wherein during or after neutralization of the organic phase containing the sulphonic acids dissolved therein but before evaporation of the volatile components of the neutralized organic phase, the ratio of the amount of water to the amount of slightly polar solvent in the neutralized phase is controlled so that this ratio is at most equal to the corresponding ratio for the azeotrope.
7. A process according to Claim 6, wherein the ratio of the amount of water to the

amount of slightly polar solvent in the neutralized organic phase is controlled to be less than the corresponding ratio for the azeotrope.
8. A process according to any preceding Claim, wherein any non-sulphonated paraffins are separated from the sulphonic acid solution prior to the addition of the slightly polar solvent thereto, by treating this solution with a water soluble polar liquid which is immiscible with the paraffins.
9. A process according to Claim 8, wherein the polar liquid is separated by distillation from the paraffin free sulphonic acid solution before treatment of the solution with the slightly polar solvent.
10. A process according to any of Claims 1 to 7, wherein any non sulphonated paraffins are separated from the organic phase containing the sulphonic acids dissolved therein by treating said phase with a water soluble polar liquid which is immiscible with the paraffins.
11. A process according to any preceding Claim, wherein the molten sulphonate is converted into a powder.
12. A process according to Claim 11, wherein the powder has a grain size ranging from 40 to 600 microns.
13. A process according to any preceding Claim 1, wherein the sulphonic acids are derived from C7 to C30 paraffins.
14. A process according to any preceding Claim, wherein the sulphonic acids are derived from C10 to C20 paraffins.
15. A process according to any preceding Claim, wherein the alkali used to neutralize the sulphonic acids is selected from hydroxides and carbonates of alkali metals, and oxides, hydroxides and carbonates of alkaline earth metals.
16. A process according to Claim 15, wherein the alkali compound is sodium hydroxide.
17. A process for separating paraffin sulphonic acids from a solution which also contains sulphuric acid and water. substantially as herein described with reference to the Example.